Regulation of gene expression at the translation level is important for many biological processes General procedures for identifying and characterizing those mRNA species that are under translational control are needed. In this project, cytosolic mRNAs will be separated into translated and untranslated species by sucrose gradient centrifugation. Radioactive cDNA copies will then be prepared from these mRNA species and used to probe high density cDNA arrays in order to identify those mRNAs that are repressed or are actively being translated. This procedure will then be tested in defining the constellation of genes that are under translational control in response to growth signals in a fibroblast cell line.